The present invention relates in general to power activated chucks, and in particular to a new and useful pressure fluid supply arrangement for chucks or similar structures which utilizes an elastically deformable seal ring.
A supply arrangement of this kind is known from German Pat. No. 16 02 813 and its corresponding U.S. Pat. No. 3545342 and have proved extraordinarily satisfactory in practice for years. The elastically deformable seal ring employed in this connection is provided with at least one passage opening designed as a throttle, and is inserted in biased state in an annular groove of a supply ring. During a pressure fluid transfer, to deform the seal ring and apply it against the circumferential surface of the chuck body, first, a certain pressure must be built up in the outer zone of the circular groove. To this end, a strong frictional force must be overcome in addition, since the seal ring applies under bias against the annular groove laterally too. This extends the time necessary for a clamping operation. Further, experience has shown that the seal ring is sometimes lifted for a short time from the circumferential surface of the chuck body, since the inner surface areas and the outer surface areas exposed to pressure during a pressure fluid transfer are almost equal in size, which results in an equalization of the pressure. This causes a sideward outerflow of the pressure fluid and, consequently, a pressure loss. Also, with the seal ring lifted, cooling water and/or chips may penetrate into the annular groove and therefrom, under supply pressure, even into the chuck and cause disturbances. Moreover, if the seal ring becomes deformed more in the middle than in the two outer portions, and thus becomes cambered, it frequently doesn't apply flatly against the chuck body. This again may unfavorably affect the pressure fluid supply. Further, particularly in chucks having a large outer diameter, the seal ring cannot be lifted satisfactorily because it is too heavy, and its side friction in the annular groove of the supply ring is too strong.